Precision inertial navigation systems typically require concentric sets of ball bearing supported gimbals which allow instruments to freely rotate in flight maneuvers and allow them to be manipulated for calibration. The embodiments of the previously referenced '6540 Application, which is herein incorporated by reference, eliminate the need for gimbals and ball bearings by supporting the inertial sensor assembly with a spherically shaped gas bearing. The gas bearing allows rotation of the inertial sensor assembly in all axes with no wear due to contact between rotating surfaces. During the flight of a craft, the angular position of the inertial sensor assembly (sometimes also referred to as the attitude, or roll, pitch and yaw of the inertial sensor assembly) relative to the frame of the craft must be monitored at all times. However, because physical contact with the freely rotating, gas bearing supported, inertial sensor assembly is undesirable, the need arises to sense the position of the inertial sensor assembly without physical contact between the sensor and the assembly.
A typical satellite mounted stellar sensor is one example of a contact free angular position sensor. A satellite mounted stellar sensor gives precise attitude information to a satellite flying in space. A star map is first programmed into the memory of the stellar sensor. Then, when the satellite needs its current attitude, it captures an image of a star field and then correlates the pattern of the stars observed to the star map in memory. By identifying the stars observed and determining the relative orientation of star field, the stellar sensor allows the satellite to determine its precise attitude in space. A stellar sensor for a satellite relies on the relative position of observable stars in outer space, which provides a relatively static and reliable source of reference points to correlate against. However, in applications where the surrounding environment is dynamic in nature, the use of external reference points is not feasible, resulting in the need for the current invention.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for a means to determine the absolute position of an object using pattern recognition.